What it means
The module detects a low input from the turbocharger or supercharger inlet pressure sensor A circuit, downstream of the throttle valve.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Sensor A measures pressure in the turbocharger or supercharger inlet passage after the throttle valve. The control module sets P012C when the sensor A signal input stays below the expected electrical range. A low input can come from a signal short to ground, poor connector contact, or a sensor fault.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
How to diagnose it
- Record freeze-frame data and check live sensor A data for a low or fixed reading, noting the engine conditions when it occurs.
- Inspect sensor A's connector and nearby harness for corrosion, damaged pins, or insulation rubbed through against ground.
- Check the sensor A reference supply and ground using the wiring diagram, since a missing supply or poor ground can affect the signal.
- Test the sensor A signal wire for a short to ground and for continuity between the sensor and control module.
- If the wiring and supplies meet the manufacturer's specification, test sensor A and replace it if it produces a persistently low signal.
Common fixes
- Repair a signal wire chafed or shorted to ground.
- Clean and secure corroded or loose sensor A connector terminals.
- Repair a faulty reference supply or ground connection.
- Replace sensor A if circuit checks show the sensor itself is pulling the signal low.
Can I keep driving?
With only the check-engine light reported, gentle driving may be possible, but avoid heavy acceleration or boost until the low signal is resolved. The module may not have dependable inlet pressure data for engine control.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.